The present disclosure relates generally to the field of aircraft radar systems. More specifically, the present disclosure relates to reducing ground clutter and/or false alerts due to RF artifacts (spurs, etc.) in aircraft radar systems.
Conventional weather radar systems emit a generally uniform, rectangular pulses of energy. The pulses reflect off a target and are received by the radar system as radar returns. Airborne weather radar systems analyze the radar returns to detect weather and other targets and to determine if certain other weather phenomena is present (e.g., turbulence, wind shear, etc.).
Generally, it is desirable to detect wind shear at lower altitudes. Detecting wind shear at lower altitudes can be difficult because signal strength of a return from a wind shear event can be relatively small when compared to ground clutter. This difficulty is exacerbated when smaller antennas are utilized.
Conventional radar systems have utilized high pass filters to remove returns associated with ground clutter. The high pass filters can have a 3 decibel (dB) cut-off frequency at approximately 200 Hz. Generally, the frequency associated with ground clutter is moved to 0 Hz so that the high pass filter can reject ground clutter returns in the receiver. The ground clutter returns are conventionally translated to 0 Hz or DC (a static return) in a post-reception process.
The post-reception process relies upon a numerically controlled oscillator (NCO) and mixes multiple frequencies to translate the return to 0 Hz. Due to numerically controlled oscillator (NCO) operations in the receiver, existing RF artifacts at DC, such as, spurs, are moved to other frequencies. As hardware ages and becomes more prone to leakage, the generation spurious signals can be more prevalent in the post-reception process. Spurious signals can appear as wind shear targets during weather target analysis and result in a false alert, caution or warning. Additionally, if a spurious signal is very strong, it can saturate the analog-to-digital (A-to-D) converter in the receiver which causes clipping. Clipping results in harmonic frequency signals which can also appear as a wind shear target and cause a false alert, caution or warning.
Thus, there is a need for a method of and a system for reducing spurious signals in radar operations. Further still, there is need for a method and a system for reducing spurious signals during wind shear detection while reducing ground clutter. Further still, there is a need for a method of and a system for wind shear detections which does not have the disadvantages associated with post-reception ground rejection processes.
There is further needed a radar system capable of reducing ground clutter without increasing spurious frequency signals. There also is a need for a radar system for and method of detecting weather phenomena, such as, wind shear events, with fewer false alerts.